Rice Genomics and Genetics 2024, Vol.15, No.3, 142-152 http://cropscipublisher.com/index.php/rgg 143 predictability of hybrid yield and nutritional quality, the identification of promising breeding lines with high iron and zinc content, as well as high yield, highlights the potential for developing biofortified rice varieties. 2 Genetic Factors Affecting Nutritional Content 2.1 Main nutritional components of rice As one of the most important staple foods in the world, rice has an important impact on human health. The main nutrients of rice include carbohydrates, proteins, fats, vitamins and minerals. Carbohydrates are the main component of rice, accounting for about 70%~80% of its total weight, mainly in the form of starch. Starch is not only an important source of energy for the human body, but also determines the texture and taste of rice during cooking. Secondly, protein is the second most important component of rice, accounting for about 7%~8% of the total weight. Although rice has a relatively low protein content, it has high bioavailability, especially a relatively high lysine content, which is very important for the growth and development of humans, especially children (Mamata et al., 2018). In addition, rice contains a small amount of fat, accounting for about 0.5%~1% of the total weight. These fats are mainly concentrated in the rice bran layer, including essential fatty acids such as linoleic acid and linolenic acid. In terms of vitamins, rice, especially brown rice, is rich in B vitamins, such as thiamine (vitamin B1), riboflavin (vitamin B2) and niacin (vitamin B3), which play an important role in human metabolism and nervous system function (Yu et al., 2009). Rice also contains a variety of minerals, such as potassium, magnesium, phosphorus and zinc. These minerals are not only important components of bones and teeth, but also participate in a variety of physiological processes in the body, including enzyme activation, acid-base balance and nerve conduction. The main nutrients of rice are diverse and balanced, and have a profound impact on human health. By understanding these nutrients, we can better understand the importance of rice in our daily diet and focus on optimizing these nutrients during rice breeding and cultivation (Mamata et al., 2018). 2.2 Genetic variation and nutritional content Genetic variation plays a vital role in the formation of crop nutrients. Genetic variation includes natural mutations and artificial selection in the genome, both of which can significantly affect the nutritional quality of crops. In natural mutations, random variations in genes may cause an increase or decrease in certain nutrients. For example, certain genetic variants in rice can increase iron and zinc levels in the grain, which could have important implications for solving the global problem of micronutrient deficiencies. Artificial selection introduces specific genetic variations through breeding techniques to improve the nutritional content of crops. Modern molecular breeding techniques, such as gene editing and genomic selection, can precisely manipulate genetic variations to enhance the content of targeted nutrients. For example, through CRISPR-Cas9 gene editing technology, specific genetic sites can be precisely introduced or deleted in rice to increase the content of key nutrients such as vitamin A, iron, and zinc. Genetic variations can also affect anti-nutritional factors in crops, such as phytic acid and tannins, which inhibit the body's absorption of nutrients. Reducing or eliminating these anti-nutritional factors through selection and breeding can significantly increase the nutritional value of crops. Genetic variation affects the nutritional content of crops through multiple pathways. Whether through natural mutation or artificial selection, genetic variation provides a wide range of possibilities and important tools for crop nutritional improvement. This not only helps improve the quality of agricultural products, but also has a profound impact on human nutrition, health and food security. Rice’s genetic diversity plays a crucial role in determining its nutritional content. Rice has significant genetic variation in traits related to nutritional content. This diversity is crucial for breeding programs aimed at improving the nutritional quality of rice (Xing and Zhang, 2010). QTL mapping has identified many loci related to rice nutritional components. For example, QTL related to grain iron, zinc and protein content have been identified, providing valuable targets for biofortification (Samonte et al., 2006). Specific QTL, such as qZn4 and qMn6.2, have been shown to affect both yield and micronutrient content, highlighting the potential to improve these traits simultaneously.
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